Effect of Medium-Energy Ar.sup.+ Ion Irradiation on the Structure of Austenitic Chromium-Nickel Steel

The effect of 15-keV Ar.sup.+ ions on the structure of austenitic chromium-nickel steel in the 3.1 x 10.sup.17-7.5 x 10.sup.17 cm.sup.-2 fluence range has been investigated in this work. X-ray diffraction analysis indicates a nonmonotonous change in the lattice parameter and the level of microstresses in some crystallographic directions with increasing fluence. The anisotropy appearance of these stresses gradually decreases and the texture becomes weaker. These processes are associated with radiation defects at the initial stage of irradiation and their radiation-induced annealing as the fluence increases. Transmission electron microscopy has revealed atomic separation in the solid solution and a decrease in the dislocation density in the steel starting from a fluence of 5 x 10.sup.17 cm.sup.-2 (40 dpa). Similar data have been obtained when steel of a similar composition has been exposed to high-energy ions. No pore formation has been detected under the used irradiation conditions, since the swelling threshold (according to known estimates, ~70 dpa) has not been reached.